Path selection schemes for routing digital data traffic among member stations or nodes of a multinode packet-switched communications network typically employ some form of shortest path or minimal delay mechanism (commonly termed a path or link metric) for determining which route is to be used to transmit data from source to destination. One such scheme, known as ARPANET (described in an article entitled "The New Routing Algorithm for the ARPANET" IEEE Transactions on Communications, Vol. COM-28, May 1980, pp. 711-719), examines the path metrics of all possible links between source and destination and selects that path through the network whose total link metric total represents the lowest transmission delay. By always basing its routing decision on the shortest path metric, the ARPANET approach tends to introduce a substantial load imbalance among the nodes and subjects the shortest path to considerable traffic congestion.
To take advantage of the substantial capacity of the network that goes unused in an ARPANET type of scheme, there has been proposed an optimal traffic assignment mechanism in which all paths through the network are employed in an effort to minimize that average delay through the network, as described in an article entitled "A Minimum Delay Routing Algorithm Using Distributed Computation" by R. G. Gallager, IEEE Transactions on Communications Vol. COM-25, January 1977, pp. 73-85. In accordance with this optimal traffic assignment approach traffic from a source is subdivided into subportions which, in turn, are routed over a number of different source-to-destination highways. As traffic is subdivided and allocated to the different paths through the network the average delay of the respective links is examined and adjustments are made (traffic is selectively moved to links having lower path delays) so as to iteratively converge upon an optimal (lowest) average delay through the network. While this latter approach improves upon the use of the resources of the network, producing a low steady state delay, it is not readily suited for use in a dynamic environment where the connectivity among nodes is subject to unpredictable transient degradation or failure.